1. Field of the Invention
The present invention relates to a toroidal-type continuously variable transmission in which an input disk is supported on a rotary shaft so as to be unrotatable with respect to the rotary shaft, an output disk is supported on the rotary shaft so as to be rotatable with respect to the rotary shaft, a trunnion, and a power roller rotatably supported on the trunnion in such a manner that it is contacted with the input and output disks.
2. Description of the Related Art
Conventionally, in such toroidal-type continuously variable transmission, in order to prevent the power roller against slippage with respect to the input and output disks, the input and output disks are energized in the mutually opposing directions by a torque cam mechanism or by an oil pressure cylinder to thereby generate a load which can be applied to the power roller. Here, as shown in FIG. 9, a trunnion 02 for supporting a power roller 01 is similar in shape to a crankshaft of a single cylinder engine, that is, the trunnion 02 has such a shape that it includes a pair of journal portions 03, 04 to be disposed on a trunnion shaft L and a U-shaped eccentric portion 05 for connecting together the two journal portions 03, 04; and, in the eccentric portion 05, there is formed an axial hole lo a for supporting the power roller 01. Therefore, in case where the trunnion 02 receives a load F from the input and output disks, it can be deformed into such a shape as shown by chained lines in FIG. 9, so that a piston 06 disposed on the end portion of one journal portion 04 can be inclined. In case where the piston 06 of the trunnion 02 is incline d in this manner, the piston 06 pries against a cylinder so that the trunnion 02 cannot be driven smoothly in the trunnion shaft L direction.
In view of t he above, in a toroidal-type continuously variable transmission disclosed in JP-A-10-331938, the rigidity of one journal portion held by and between the piston and eccentric portion of a trunnion is lowered and the lowered-rigidity portion is deformed to thereby prevent the piston against inclination.
However, as in the toroidal-type continuously variable transmission disclosed in JP-A-10-331938, to lower the rigidity of the journal portion of the trunnion is not desirable in securing the strength of the trunnion and, in addition to this, there is a possibility that the flexed trunnion can give rise to the lowered transmission response characteristic of a toroidal-type continuously variable transmission.
The present invention aims at eliminating the drawbacks found in the above-described conventional toroidal-type continuously variable transmission. Accordingly, it is an object of the invention to provide a toroidal-type continuously variable transmission which is simple in structure and can enhance the rigidity of a trunnion.
In attaining the above object, according to a first aspect of the invention, there is provided a toroidal-type continuously variable transmission, comprising: an input disk supported on a rotary shaft so as to be unrotatable with respect to the rotary shaft, an output disk supported on the rotary shaft so as to be rotatable with respect to the rotary shaft, a trunnion, and a power roller supported rotatably on the trunnion in such a manner that it is contacted with the input disk and output disk, the trunnion comprising a pair of journal portions disposed on a trunnion shaft and spaced from each other, a U-shaped eccentric portion disposed eccentric from the trunnion shaft and having two ends integrally connected to the mutually opposing end portions of the pair of journal portions, and a pivot shaft disposed in the eccentric portion for supporting the power roller in a space defined by the eccentric portion and the mutually opposing end portions of the pair of journal portions, wherein the trunnion is moved in the direction of the trunnion shaft and is rotated around the trunnion shaft to thereby shift the contact positions of the power roller with the input disk and output disk for transmission, wherein the mutually opposing end portions of the pair of journal portions are connected together by a reinforcing member, and the power roller is held by and between the eccentric portion of the trunnion and reinforcing member.
According to the above structure, the mutually opposing end portions of the pair of journal portions respectively connected to the two ends of the eccentric portion of the trunnion are connected together by the reinforcing member and are thereby enhanced in rigidity. Therefore, even in case where a load is applied from the input and output disks to the eccentric portion of the trunnion through the power roller, the deformation of the trunnion caused by the load can be controlled down to a minimum. Thanks to this, not only occurrence of frictional actions in the support portion and drive portion of the trunnion can be prevented, but also the movement of the trunnion in the trunnion shaft direction as well as the rotational movement thereof around the trunnion shaft can be carried out smoothly.
Also, according to a second aspect of the invention, there is provided a toroidal-type continuously variable transmission, in which, in addition to the structure according to the first aspect of the invention, oil passages for supplying lubricating oil, which is used to lubricate the contact portions of the input disk and output disk with the power roller, are formed in the reinforcing member.
According to the above structure, since the contact portions of the input disk and output disk with the power roller are lubricated with the lubricating oil that is supplied through the oil passages formed in the reinforcing member, the input disk, output disk, and power roller can be enhanced in durability.
By the way, an input shaft shown in an embodiment of the invention to be described later corresponds to the rotary shaft specified in the patent claim of the invention.